We have the following:
[tex]f(x)=-x+5[/tex]therefore, f (x) = 3
[tex]\begin{gathered} 3=-x+5 \\ x=5-3 \\ x=2 \end{gathered}[/tex]the answer is x = 2
f (x) <= 3
[tex]\begin{gathered} -x+5\leq3 \\ -x\leq3-5 \\ -x\leq-2 \\ x\ge2 \end{gathered}[/tex]The answer is x => 2